Want to use Google Voice on your mobile phone? Google has apps for Android, the iPhone, and BlackBerry.

But a year-and-a-half after Windows Phone launched, Google still has no plans to support Microsoft's mobile platform.

"We're focusing our Google Voice efforts on Android & iOS and don't have a plan to extend this to the Windows Phone," Google told me via e-mail, when I asked recently about the lack of support. "This may change if we start to see greater demand from Windows Phone users for Google Voice."

Why bother? Let me count the reasons...
With Windows Phone having only a 4 percent share of the smartphone market behind Android, iPhone, and BlackBerry, it's easy to say that Google should be excused for ignoring the platform. But looking at only market share doesn't paint a complete picture of why Google skipping Windows Phone is odd.

For one, Google did decide Windows Phone was important enough to create an official Google Search app for the platform, even though you can easily use Google Search through the Windows Phone Web browser. Google even encourages people visiting Google.com to pin its search page to their Windows Phone start screen. Apparently, Windows Phone does matter to Google.

More important, Google wasn't happy about Apple rejecting its Google Voice app back in July 2009. It wanted Google Voice to be on more than just the Android and BlackBerry platforms. So why not build an app for the Windows Phone platform, which, unlike Apple, says it would welcome the move?

"Windows Phone Marketplace features apps submitted by Google today, and we'd be happy to publish additional Google titles," Microsoft e-mailed me, when I asked about why there was no official Google Voice app and if there was any Microsoft issue preventing one from appearing.

How the Web-based version of Google Voice for mobile lost its groove
Perhaps it wouldn't be so bad if the Web-based version of Google Voice for mobile that Google initially launched still worked right. Announced in January 2010, it allowed iPhone users, as well as Palm WebOS users, to make phone calls using a dialer through Google Voice.

It wasn't as good as having an actual app. You couldn't access your contact book, for example. But you could easily make outbound calls using your own Google Voice number.

Apparently after Apple relented and finally allowed the official Google Voice app into its app store, Google decided that a full-featured browser-based version of Google Voice for mobile was no longer needed.

Try to visit that site today in the iPhone or Android, and you're told to download the Google Voice app. Try to visit it using Windows Phone, and you're redirected to a stripped-down version of Google Voice for mobile that lacks a keypad for dialing. There's no support for showing your Google Voice number to callers, either. Other features are gone as well.

None of this is Windows Phone-specific, by the way. You get the same poor, stripped-down experience if you log in using the browser on the iPhone or Android. Google appears to have dropped functionality that the Web-based version used to offer all mobile users, it appears.

That's disappointing. Google has pushed for Web-based apps as a way for any company to provide universal support of its products and services, regardless of operating system platform. Its HTML 5 mobile version was doing that for iPhone users, before there was an iPhone app. It could continue to do so for Windows Phone users, if Google would restore the functionality that was there before and still claims to provide on the Google Voice for mobile home page:

Google

Who wants my password?
This leads to the security issue. Since the Web-based version is bad, Windows Phone users looking for a Google Voice app as an alternative will find only unofficial apps in the Windows Phone Marketplace. These apps require providing your Google Voice username and password to use.

Whoa. This isn't a case of handing over something like your Twitter username and password and potentially putting a single service that you use at risk. A "Google Voice" account is really a "Google" account, which may give someone access to your e-mail, your search history, credit card information, and more.

Do these apps keep any record of your username and password? Are they encrypting your connection? GoVoice and GV For Windows Phone are two unofficial Windows Phone apps that don't make this clear.

GoVoice says: "We take your privacy seriously and we don't store your password on the device unless if you choose to do so. Even if your device is compromised you can still revoke GoVoice's access." But if the password isn't stored on my device, is it on GoVoice's server? Or where?

GV For Windows Phone says: "Your password is encrypted on the device and only sent to the Google Voice servers over Secure Sockets Layer (https). We care about your security." That's encouraging, but does GV see a copy? And is the secure connection maintained?

Maybe these applications are perfectly safe, but I'd feel more comfortable using an application directly from Google itself or at least having the Web-based version it previously offered working again. Here's hoping for either. Google Voice is a great service that I've used for ages. I'd like it for all the phones I own -- Android, iPhone, and Windows Phone.